Electronic percussion instrument having interposed rhythmic patterns each with its own tone color



April 16, 1968 H. HURVITZ Original Filed Jan. 15, 1964 ELECTRONIC PERCUSSION INSTRUMENT HAVING INTERPOSED RHYTHMIC PATTERNS EACH WITH ITS OWN TONE COLOR M '5 A/Ww[/ A/W J SAuJTOOT H v yum BA GEN AMP 23 sucEQ L m B7 l!\ k TEMP o Avc 35 I S LENPGQI'LHSEEN E2 7L SYNC PEAK PULSE DETECTOR 53 M \2 r '32 3O 2 I 3; 38 .g u 32 02 39 SOUND RECORDER INVENTOR HYMAN Hu EVITZ ATTORNEYS United States Patent ELECTRGNIC PERCUSSIUN WSTRUMENT HAV- ING ENTERPGSED RHYTHMIC PATTES EACH WITH ITS OWN TONE COLOR Hyman Hnrvitz, Washington, ll).C., assignor to l). H. Baldwin Company, Cincinnati, Ohio, a corporation of Ohio Continuation of application Ser. No. 337,820, Jan. 15, 1964. This application Mar. 17, 1966, Ser. No. 541,890

7 Claims. (Cl. @4-128) ABSTRAQT OF THE DISCLQS A rhythmic interpolator in which rhythmic patterns are read off a cyclic record and each pattern is associated with its own tone color or voice, which may be the same or different, so that a pattern in a first voice may be interpolated with a different pattern which itself has a different voice.

This application is a continuation of my prior application Ser. No. 337,820, filed Jan. 15, 1964, entitled, Electronic Percussion Instruments.

The present invention relates generally to electronic percussion instruments, and more particularly to systems for simulating drums, cymbals, marimbas and the like devices for producing percussive sounds, in any desired rhythm and tempo and in synchronism with actuations of a control device.

It is well known to produce the sounds of percussion instruments by electronic circuitry, and to do this in a rhythm controlled in synchronism with music as played by a musical instrument. Since the musical instrument may be played in any desired tempo, the percussion simulator must be capable of maintaining synchronization, automatically, in both frequency and phase for a wide range of tempos. But accomplishing synchronism is only a small part of the problem, because of the large number of possible percussion devices which are commonly employed in present day bands, and the large number of different and exotic rhythms which must be interpolated between the beginning and termination of each measure of music. When one attempts to design an electronic percussion simulator, then, one is led to a complex device, the cost of which is such as to render the device uneconomic in most circumstances.

It is an object of the present invention to provide an electronic percussion simulator which includes a simple motor control system for synchronizing a percussion tone generator with closures of a switch, maintaining precise synchronism in both frequency and phase, the tone generator being photo-electric, and containing pre-recorded percussion sounds of all desired types, in all desired rhythms, without requiring undue complexity in the electrical or mechanical arrangement.

The above and still further objects, features and advantages of the present invention will become apparent upon consideration of the following detailed description of one specific embodiment thereof, especially when taken in conjunction with the accompanying drawings, wherein:

FIGURE 1 is a block diagram of a phase and frequency synchronization system, utilized in the invention for controlling rotation of a percussion generator in the form of a tone disc;

FIGURE 2 is a block diagram of a system for maintaining sawtooth waves at constant amplitude;

FIGURE 3 is a schematic representation of a tone generator according to the invention; and

FIGURE 4 is a schematic representation of a tone disc recorder.

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In the drawings, 10 is a DC source, connected in series with a manual switch 11 and a sync pulse generator 12. Each closure of switch 11, which may be accomplished in time with polytonic music, generates a sync pulse of predetermined amplitude and duration, regardless of duration of switch closure. The sync pulses synchronize a sawtooth generator 13, to produce one sawtooth (or two or three, etc.) per sync pulse. The generator can be adjusted to have a natural frequency well below the sync rate, or at twice that rate, etc. Assume that the sawtooth rate is always near the sync pulse rate. Then as the sync pulse rate increases or slows, the sawtooth will follow, within quite wide limits. The switch 11 may be closed in synchronism with polytonic music, say at the beginning of each measure. If so, the sawtooth generator 13 follows as the music goes from allegro to andante, etc., but if not the sawtooth frequency can be roughly adjusted to the new rate. To facilitate adjustment the generator 13 is provided with a manual frequency control 15, adjusted to various standard tempi, as allegro, allegretto, andante, etc. and the sync pulses need only adjust for the variations from the standard which are peculiar to an individual musician or band, say about 25%.

The sawtooth pulses provided by generator 13 are detected in a peak detector 16, which is followed by a pulse lengthener 16a, to provide a reference level signal at lead 17, proportional to the tempo. This signal is used to control the gain of an amplifier 18 of the output waves 19 of generator 13 in such manner as to maintain these equal at all times, by increasing gain as amplitude of waves 19 decreases, and vice versa. This expedient is required in order to provide constant amplitude sawtooth waves for all tempi, i.e. regardless of peak amplitudes of waves 19.

An alternative expedient is shown in FIGURE 2, where the peaks of the sawtooth output of amplifier 18 are compared with a fixed DC value, provided by reference source 21 in a comparator 22. The difference voltage provided by comparator 22 is used as an AVC voltage for amplifier 18 and maintains its output constant as wave form 19 varies in peak amplitude.

In any event, sawtooth waves 2t) of constant amplitude but variable frequency and phase, appear at the output lead 23 of amplifier 18. These proceed to a slicer 35.

A DC motor 30 drives a tone disc 31. Shaft position of the tone disc, i.e. its zero phase, is sensed by brush 32, in conventional fashion, to provide a very short pulse 33, for each revolution of the shaft 34, when it attains a zero phase position. This pulse is a sampling pulse, applied to the slicer 35, and serves to sample the then amplitude of sawtooth wave 20. Assuming that the motor makes one revolution per sawtooth wave, the sample 36 will have an amplitude which is a function of the relative phases of the sampling pulse and the sawtooth. The output of the slicer is smoothed in a pulse lengthener 37, and the smoothed pulse is applied to the grid 38 of a triode amplifier 39, the anode voltage of which is applied to a speed control circuit of motor 30.

If the motor departs in frequency from the sampling pulses, 33, the sampled pulses 36 will vary in amplitude from pulse to pulse, due to progressive shift of relative phase. This will progressively increase the voltage at grid 38 and decreases the control signal to DC motor 30 as motor phase advances from cycle to cycle, and this will slow the motor. The opposite effect occurs if the motor is too slow. If motor speed is correct but phase is too far advanced or too far retarded, the pulses 36 will not tend to remain of constant ampltiude, because incorrect phase has the same effect as incorrect speed. Hence, incorrect phase will cause an increase or decrease of speed until phases align, i.e. correct speed occurs for only one value of phase.

Motor control circuits of the general type described are per so old, but have not heretofore been employed in response to synchronized sawtooth voltages of variable frequency and amplitude.

The known motor control system operates from sawtooth waves of fixed frequency and amplitude, and the slicer operates into an integrator. This system is not feasible for use with a sawtooth wave which can vary widely in frequency, since the integrated value depends on both input amplitude and frequency of signals applied to the integrator, and if both vary independently of motor speed, cannot operate correctly. Applicants pulse lengthener lengthens each sampled pulse until the next sampled pulse appears. Therefore, the control signal applied to the motor 30 during each revolution has the same level value during each rotation of the motor shaft 34 regardless of motor speed. When 'motor speed and phase is correct a steady DC control voltage of correct amplitude is being applied, and this tends to remain the same for all correct or synchronized speeds and phases.

Assuming correct motor speed, any departure from correct phase, from immediately following initiation of sampling pulse 33 until the next sampling pulse 33 occurs, applies a correcting control voltage to motor 30. Variation of the anode resistance 42, by means of control 160 of amplifier 39 effects speed or phase adjustment, if needed, i.e. as circuit values change with time or temperature, or supply voltage, or to comply with radical changes of speed at switch 11, or to make initial adjustments of phase. Preferably control and Mill should be ganged or similarly calibrated. The load on the motor 30 remains essentially constant, regardless of speed variations so that accurate and rapid control can be achieved readily if severe inertial effects do not intervene.

Assume now that motor speed and phase are synchronized with closure of switch 11, and proceed to FIGURE 3, which shows the face of tone disc 31.

Tone disc 31 contains recordings of actual percussion tones as played by a live drummer, a different percussion instrument or rhythm appearing at each radius, as 50, 51, 52. Each separate track is illuminated by a separate lamp, as 60, 61, 62, energized selectively at will via manual switches 70, 71, 72 from a power source 75. Illumination takes place via very narrow radial slots 8t), 81, 82 and light proceeds from the lamps via the slots 8t), 81, 82 to photo-cells 90, 91, 92 (or to one cell for all lamps), the output of which are combined in amplifier 95, which drives a speaker 96.

So, if switch 72 is closed, lamp 62 is energized, and illuminates track 52 via narrow radial slot 82, the light proceeding through the track 52 to photo-cell 92, which translates the light variations into sound at speaker 96.

The tracks, as 52, were initially recorded by standard sound-on-film recording techniques, on a photo-sensitized disc 97 (FIGURE 4), the recorder being indicated at 93, and are transferred to track 50 photographically. Any sound or film recording technique can be employed, i.e. variable density or variable height sound track. The tracks are made by a living drummer, playing actual instruments, as blocks, cymbals, marimbas, traps, etc. in time to actual music. There are no problems of providing re-entrant tracks, in this case, and the tracks have a living quality which is absent from synthesized percussion tones, due to slight irregulatrities of timing, style, quality etc. which occur in human performances. The reproduced music therefore is attractive, and cannot be distinguished from performance by a living artist. Since various drummers have different distinctive touches and styles, any of these can be provided, a feature which is attractive to the co noscenti.

Plural tracks may be combined as desired, for example, bass drum, traps and marimba, and each track may have the same or a dilferent rhythum but always the same tempo. The system can be expanded by providing plural discs and the construction may be in accordance with the teaching of Williams, in Us. Patent No. 3,003,383.

The motor control system of FIGURE 1 is essentially a phase control system, and speed is controlled only in terms of phase, i.e. a progressive phase shift occurs with speed, if it is unsynchronized. For use in the present application it is requisite that phase be always correct. This condition is accomplished, at least to a good approximation, because the amplitude of sawtooth wave 20 is corrected during each measure according to the peak value of the sawtooth wave 19 in the preceding measure, since it is the value which varies gain of amplifier 18. Pulse lengthener 16a sets a steady value each time that a new reference value arrives, i.e. each time that a preceding peak is attained.

The system is described as providing one sawtooth wave per sync pulse, and one control pulse 33 per revolution of motor shaft 34 In fact, the sawtooth generator 13 can be synced at a multiple frequency, and a corresponding number of control pulses 33 can be provided, per revolution of shaft 34, with no increase of complexity of the system. For example, if switch 11 is closed three times per measure, and if three pick-off points on shaft 24 are provided, at intervals, complete correction of phase will occur three times per revolution of discs 31. This permits change of tempo in one third of a measure of music. Normally, however, correction once per measure is adequate.

Some ditiiculty may arise due to inertia of motor 30 and disc 31, i.e. the motor may not respond as rapidly as desired to changes of control signal. This can best be compensated by using a small motor Stl and a light weight disc 31.

If a sudden change in tempo occurs, one measure of error occurs, since each measure of percussion tones is timed by the preceding measure if one sync pulse per measure is employed. Therefore, if the system must be employed with music which varies rapidly in tempo, and if no time can be allowed for the percussion system to attain sync condition, it is necessary to provide plural sync pulses per measure, as hereinabove suggested, since thereby timing error will subsist for a like fraction of a measure (subject to effects of inertia).

While I have described and illustrated one specific embodiment of my invention, it will be clear that variations of the details of construction which are specifically illustrated and described may be resorted to without departing from the true spirit and scope of the invention as defined in the appended claims.

What I claim is:

1. A percussion tone generating system, comprising a periodically rotatable pre-recorded source of tone tracks, containing plural re-entrant tracks each representing one musical measure of percussion tones in a predetermined rhythm, stationary read out means for selectively reading out said tracks at will, a control element actuable in time to music of variable tempo, and means responsive to said control element for synchronizing in both frequency and phase the periodic rotations of said source with respect to actuations of said control element.

2. The combination according to claim 1 wherein said tracks are pro-recorded from live percussion tones.

3. The combination according to claim 1 wherein is provided a direct current motor for rotating said rotatable pro-recorded source of tone tracks, a source of direct current control signal for said motor, and means for varying the amplitude of said control signal in response to relative phase and speed deviations of said control element and said source, in such sense as to maintain speed and phase synchronism.

4. A music system, comprising a source of sync signals of variable rates, a source of sawtooth voltage waves, means responsive to said sync signals for synchronizing said sawtooth voltage waves, said sawtooth voltage waves having variable amplitudes as a function of said rates for all said rates, means for equalizing the amplitudes of said sawtooth waves, a direct current rotatable motor,

means responsive to each rotation of said motor for amplitude sampling the equalized sawtooth waves, and means responsive to the samples for controlling the speed and phase of rotation of said motor, a tone track disc driven by said motor and having plural tone tracks, and means for reading out said tone tracks selectively at will, whereby said tone track disc is synchronized with said sync signals in both speed and phase, at said variable rates.

5-. A percussive tone generating system, comprising a periodically rotatable pre-recorded source of discrete spaced signal tracks, containing plural re-entrant tracks each representing one musical measure of signals in a predetermined percussive rhythm, stationary read out means for selectively reading out said tracks at will, a control element actuable in time to music of variable tempo, and means responsive to said control element for synchronizing in both frequency and phase the periodic rotations of said source with respect to actuations of said control element.

6. A percussive tone generating system, comprising a periodically rotatable pre-recorded source of discrete spaced signal tracks, containing plural re-entrant tracks each representing one musical measure of signals in a predetermined percussive rhythm, stationary read out means for selectively reading out said tracks at will, a control element actuable in time to music of variable tempo, and means responsive to said control element for synchronizing in both frequency and phase the periodic rotations of said source with respect to actuations of said control element, wherein is provided a direct current motor for rotating said rotatable pie-recorded source, a source of direct current control signal for said motor, and means for varying the amplitude of said control signal in response to relative phase and speed deviations of said control element and said source, in such sense as to maintain speed and phase synchronism.

7. A music system, comprising a source of sync signals of variable rates, a source of sawtooth voltage waves, means responsive to said sync signals for synchronizing said sawtooth voltage waves, said sawtooth voltage waves having variable amplitudes as a function of said rates for all said rates, means for equalizing the amplitudes of said sawtooth waves, a direct current rotatable motor, means responsibe to each rotation of said motor for amplitude sampling the equalized sawtooth waves, and means responsive to the samples for controlling the speed and phase of rotation of said motor, a percussion track disc driven by said motor and having plural percussion tracks, and means for reading out said percussion tracks selectively at will, whereby said percussion track disc is synchronized with said sync signals in both speed and phase, at said variable rates.

References Cited UNITED STATES PATENTS 2,563,816 8/1951 Butman 328-133 2,576,760 11/1951 Jones et a1. 84--1.18 3,003,383 10/1961 Williams 841.26 3,022,695 2/ 1962 Williams 84-1.26 X 3,146,290 8/1964 Park 84--1.03 3,150,227 9/1964 Ziehlke 84--1.28 X 3,175,161 3/1965 Hackborn et a1. 328- 3,197,543 7/1965 Williams 84--1.28 3,207,835 9/1965 Holman et al 84-1.26 X 3,214,507 10/1965 Williams 84-1.26 X

ARTHUR GAUSS, Primary Examiner.

R. H. PLOTKIN, Assistant Examiner. 

